Allison vibration

[RJohn]

My 45' Monaco is shuttering when the RPM's drop to around 1300 waiting for a downshift. If I manually downshift it goes away. My question is, has anyone experienced this problem? Could it be a engine problem rather than the transmission? I have changed both fuel filters.

[OneRVer]

When was the last time you serviced the tranny?

[RJohn]

Coach is an 09 Monaco w/28K miles. Unless I'm mistaken, tranny is not due for service.

[Steve Ownby]

How are you aware of this shutter? Can you feel it in the steering or actually in the body of the motorhome as a "shaking"? Or is it something you hear. Is it between every downshift or just certain gears? Is it during heavy throttle conditions or any downshift?

A couple of years ago I did not lube my drivetrain for about 10K miles and I started noticing a vibration at a certain speed in a certain gear. I lubed my U joints and drive shaft spline and it went away.

If you are concerned and it continues, you are still under warranty on both engine and transmission. A trip to a Cummins or Allison dealer might be the best.

[RJohn]

Thanks for the reply Steve, I have already taken the coach to the dealer

[speed racer]

I would have the ride height checked. These units have a very short drive shaft and any missalighnment can cause this problem.

[Norm4015]

I agree with the drive shaft theory. If the U joints or slip joint get dry you will get the vibration. I know.

[RJohn]

Turns out I had a bad injector on the motor. That explains the loss of power and fuel mileage, nto to mention the shudder.

Thanks to everyone for their responses.

[JohnRR]

Quote:

Originally Posted by RJohn Turns out I had a bad injector on the motor. That explains the loss of power and fuel mileage, nto to mention the shudder. Thanks to everyone for their responses.

Thank you for the update, many times like this one I think the outcome is just as valuable or more so than the original question.

[hzjcm8]

Quote:

Originally Posted by RJohn Turns out I had a bad injector on the motor. That explains the loss of power and fuel mileage, nto to mention the shudder. Thanks to everyone for their responses.

John,

Just to follow up. You might want to check your engine oil using oil analysis. There's a good chance the injector was bleeding fuel into the oil. When this happens, it lowers the oil viscosity and can produce wear if left unchecked.

[OneRVer]

Quote:

Originally Posted by hzjcm8 John, Just to follow up. You might want to check your engine oil using oil analysis. There's a good chance the injector was bleeding fuel into the oil. When this happens, it lowers the oil viscosity and can produce wear if left unchecked.

You are right John. Since 2007 due to the EPA regulation this has been a problem on diesel engines. Thanks for the heads up. I do an engine analysis every year. Shoot for $15.00, why not.